April 24, 2017

Cassini snaps beautiful photo of Earth before final ‘death dive’

This weekend marks the beginning of the end for Cassini, as after 13 years of studying Saturn and its moons, the NASA spacecraft will change course, complete one final flyby of the moon Titan, and ultimately plunge to a fiery demise in the atmosphere of the gas giant itself.

Cassini, which began its journey over two decades ago, facilitated the publication of more than 3,000 scientific papers with the data it collected and is responsible for several major discoveries, including liquid methane seas on Titan and evidence of hydrothermal activity on Enceladus.

Now, as its mission comes to an end, the spacecraft will change course, during which it will once again complete a close flyby of Titan, the US space agency explained. This will allow Cassini to make the first of 22 dives between Saturn and its innermost ring, the New York Times said, making it the first human spacecraft to ever pull off such a feat.

Those 22 dives will continue on a weekly basis through the summer, and on September 15, the spacecraft – which is nearly out of fuel – will eventually succumb to Saturn’s gravity and enter the planet’s atmosphere, where it will likely be incinerated as it hurtles towards the surface.

No need for a eulogy just yet, though, say mission scientists

Before any of that happens, however, Cassini still has work to do. First, on Saturday, it will perform its 127th flyby of Titan. That maneuver, NASA told USA Today will be the probe’s “final  opportunity for up-close observations of the lakes and seas of liquid hydrocarbons that spread across the moon's northern polar region, and the last chance to use its powerful radar to pierce the haze and make detailed images of the surface.”

However, according to The Verge, the maneuver will also cause Cassini to be within around 1,840 miles of Saturn’s atmosphere – its closest ever orbit around the gas giant and the height from which it will complete its 22 “Grand Finale” orbits. Program manager Earl Maize told the website that he has “no doubt” that Titan’s gravity will help Cassini shift into the correct final orbit, but that his team is unsure what lies in the gap between Saturn and its rings.

Since the region is unexplored, there is some concern that debris from the rings could knock Cassini out before it completes all of its maneuvers. In fact, the team explained that they would not even immediately know if it even survived its first journey through the ring gap, as a status message sent by Cassini won’t even arrive on Earth until approximately a day later.

If all goes well, Cassini will repeat that orbit on a weekly basis until September 15, collecting samples of Saturn’s atmosphere and measuring its mass and weight in the process, according to The Verge. Through its travels in the ring gap, scientists hope that Cassini will help differentiate between the weight of Saturn and the weight of its rings. They also hope to study “ring rain,” particles that escape from the gas giant’s rings and flow into the planet itself, the website noted. This should provide new insight into the composition of those rings.

“I think it is too early to eulogize Cassini on the occasion of its death, as incineration is five months away,” Jonathan Lunine, director of the Cornell Center for Astrophysics and Planetary Science and a longtime member of the Cassini mission team, told USA Today. “Between now and September, there will be a ton of new science on what’s inside Saturn, how much the rings weigh, and amazing detail on rings, ring-moons and atmosphere.”


Image credit: NASA-JPL